The invention relates to a method for determining an exhaust gas recirculation amount for an internal combustion engine, particularly an internal combustion engine for a motor vehicle.
The use of exhaust gas recirculation offers advantages with regard to fuel consumption and exhaust gas emissions.
DE 199 34 508 A1 discloses a method for controlling the exhaust gas recirculation wherein a desired exhaust gas recirculation amount is determined on the basis of engine load, engine torque and air pressure, an actual exhaust gas recirculation amount and the opening and closing movement of a throttle valve are determined by sensors and an exhaust gas recirculation control valve is operated depending on the difference between the actual and the desired exhaust gas recirculation amount and a throttle valve opening signal as well as a throttle valve closing signal and the air pressure present at the time. The exhaust gas recirculation amount is determined by measuring the differential pressure in a throttle opening provided in a respective exhaust gas recirculation line.
Often, particularly in connection with Diesel engines, particle filters are provided in the exhaust duct of a motor vehicle in order to keep the exhaust gas emissions at a low level. The exhaust gas back pressure depends on the charge of the particle filter so that the exhaust gas back pressure may change significantly depending on the charge of the particle filter, which may result in disturbances in the control of the outer exhaust gas recirculation amount and cause a deterioration in the accuracy of the control.
It is the principal object of the present invention to provide a method by which the exhaust gas recirculation amount can be accurately and reliably determined under various motor operating conditions, particularly with the use of a particle filter.
The word “amount” is used mainly for simplicity reasons and comprises any physical value indicating an amount, such as the mass or the amount or mass rate for a re-circulated exhaust gas or gas mixture supplied to the engine.